Hydrogenation of pressure tar



Filed May 21, 1930 IIIIIII IIOIII i lnUerJFfi": Robert E wilson Patented May 29, 1934 I r I 1 UNITED; STATE PATENT oFncE I, "IIIYDRQGENATIONOFPRESSURETARI Robert E. WilsomChicago, Ill., assignor Standand Oil Company (Indiana), Chicago, ,,I ll., a

corporation of Indiana Application May 21, 1930, Serial No..:454,244

' 7 Claims. (Cl.196

This invention relates to the iormationpi gaso-, drogenzcarbon ratio of about 1.7 to 1.85; exline by the hydrogenation of heavy hydrocarbon amples of clean stocks are Mid-CQntimnt crude oils, and especially those of high coke forming with a ratio of 1.84, 37 B. gas oil with aratio tendencies, such as reduced pressure tar. of 1.86, 60% reduced Mid-Continent crude with a 5 Pressure-tar is obtained in oil refineries as a ratio of 1.75, and pressure tar distillate with a 60 byproduct from cracking processes which are carratioof 1.69. Reduced pressure tar is an example ried out under pressure. When this heavy oil or of an oil with a tendency to coke, and its atomic tar is heated to temperatures high enough for hyhydrogen: carbon ratio is about 1.10 to 1.45. drogenation, coke or carbon very quickly deposits In the accompanying drawing I have shown 19 on the walls 'oithe heater, in valves and return diagrammatically a system for carrying out my 65 bends, etc. This carbon formation or coking" is invention.

detrimental because it cuts down'the eifective Pressure tar from storage tank 10 is. passed heat transfer, impairs the circulation, and frethrough pipe 11, pressure pump 12, pipe 13, mixer quently necessitates a shut-down for cleaning. 14, heat exchanger and pipe 16 to the heating 1 While the presence of hydrogen under high prescoils 17 of pipe still 18, the hot fluid being dis- 70 i sure tends to prevent coke deposition, stocks like charged through pipe 19 into the base of catalyst pressure tar have been so highlycracked and are chamber 20. Simultaneously, a clean charging so prone to deposit coke,- that coke deposition stock, such as gas oil, is taken from storage tank takes place before the stocks have an opportunity 21 through pipe 22, pressure pump 23, pipe 24,

to be hydrogenated. The object of my invention mixer 25, heat exchanger 26, and pipe 27 to heat- 75 is to providea system for hydrogenating pressure ing coils 28 of pipe still 29, the heated mixture tarand similar coke forming oils which will avoid being discharged through pipe 31, mixed with the the deposition of carbon in .the tubes or other contents of pipe 19, and discharged in the base of parts of the system. catalyst chamber 20. h

In my improved system I heat the pressure tar The catalyst chamber may be an elongated, 80

' to a temperature of about 650 to 750 F; (below cylindrical vessel containing a catalyst 31 held on coking temperature) in an elongated, closed conscreens or trays 32. The catalyst is preferably a duit, and I simultaneously heat a noneeking metal or an oxide of a metaloi the sixth group of liquid to a temperature of about 850 to 950 F. I the periodic system, or mixtures ofsuch metals then mix the not pressure tar withthe other and/or oxides; for example, nine parts of chro- 85 heated liquid in such proportions that. the resultmium oxide and one part of molybdenum oxide.

ing temperature is from 750 to 850 F., the tem- Such catalysts are not poisoned by sulfur and are perature depending upon the nature of the suitably classified as sulfactive hydrogenation catalyst, the nature of the charging stock, and catalysts. The catalyst maybe supported in any the desired end product. Since the temperature conventional way, and may be held on a plu- 90 of the pressure tar is below coking, there will be rality of trays, or even circulated by the liquid it no deposition of carbon in these tubes. As a the conditions are such that the fluids in the refurther safeguard, I increase the velocity and action chamber are in the liquid phase. turbulence ln-the pressure tar heater by mixing. Hydrogen and reaction products from the catamore hydrogen with the pressure tar than with lyst chamber are conducted by pipe-33 through 96 -the clean charging stock. By regulating the pipes 34 and 35 to heat exchangers l5 and 26 in amounts of diiierent charging stocks and simulamounts regulated by valves 36 and 3'7. I prefer i taneously regulating the amount of hydrogen into use separate heat exchangers because the prestrcduced into each charging stock and the temsure tar may be heated to a lesser degree at this peratures to which charging stocks are heated," I point and it may also be mixed with an unusually can effectively eliminate coking in the pipe sti1l,. large amount of hydrogen, as will be hereinafter and yet bring the pressure tar to the desired tempointed out. The reaction products'leave the heat perature for hydrogenation. exchangers by pipes 38 and 39, and are then cooled The non-coking liquid used may suitably be a in condenser "coil40 which liquefies gasoline and '50 light stock as light gas oil or naphtha bottoms, heavier hydrocarbons. The condenser coil may or a heavy, slow cracking distillate stock such as be immersed in a suitable cooling fluid held by pressure tar distillate. The atomic ratio of hytank 41, the cooling fluid being introduced and drogen to carbon is an index of the tendency to withdrawn by pipes 42. coke or deposit carbon. Acleanstock, one which The cooled, liquids are discharged by pipe 43 55 has no appreciable tendency to coke, has a hyinto liquid separator 44, where condensed liquids are separatedout and removed by through reducing valve 47.

The gases from separating tank 44 are conducted by pipe 48 to the base of scrubber tower 49, which may be filled by packing material 50 held by screen 51 The liquid 52, which is circulated in the scrubbing tower, collects in the base thereof and is withdrawn by pipe 53 through reducing valve 54 into a gas release tank 55, the gases, such as hydrogen sulfide, methane, etc. being discharged through pipe 56. The liquid from the base of gas release tank 55 is circulated through pipe 57 by high pressure pump 58,,which forces pipe 46 it through pipe 59 and nozzle 60. This nozzle sprays the liquid onto the packing material countercurrent to the upward flow of gases, which purifies the hydrogen for further use in the system. The scrubbing liquid is preferably an absorptive, nonvolatile oil.

The hydrogen leaving scrubber 49 by pipe 61 is compressed to 200 atmospheres by compressor 62. It is then mixed in pipe 63 with make-up hydrogen from high pressure line 64 in amounts ,regulated by valve 65. The compressed hydrogen is introduced through pipe 66 into the pressure tar charging stock, and is simultaneously introduced through pipe 6'7 into the gas oil charging stock, the relative amounts of hydrogen being regulated by valves 68 and 69, respectively.

.The operation of my invention will be obvious from the above description. A larger amountof hydrogen is preferably mixed with the pressure tar than is mixed with the gas oil because this produces a more turbulent and more rapid flow of the pressure tar through the exchanger and through the pipe still, thereby minimizing the danger of coke formation in the pipes.

The pressure tar is heated in. pipe still 18 to a temperature below that at which coking occurs,

that-is, to about 650 to 750 F. Simultaneously, the clean charging stock is heated in pipe, still 29 to a temperature of about 850 to 950 F. so that the mixture will have a temperature of about 750 to 850 F. I thus avoid high temperatures in the pressure tar pipe still and at the same time I supply the heat necessary for cracking and bydrogenating this material in the catalyst chamber. Coke deposition may be substantially retarded either by using a lower temperature in pipe still 18 or by increasing the amount of hydrogen which is mixed with the pressure tar and thereby increasing its velocity through the pipe still. I prefer to combine these expedients and avoid all possible coking trouble.

While I have described a preferred embodiment of my invention, it is understood that I do not limit myself to the details therein set forth except as defined by the following claims.

Wherever the terms fhydrogenation or hydrogena-ting are used herein they shall be understood to refer to processes of so-called destructive hydrogenation in which hydrocarbon materials are treated in the presence of hydrogen at elevated temperatures and high pressures with or without catalysts, said conditions being such as to result not merely in simple hydrogenation of unsaturated molecules to produce saturated ones, but in deep-seated transformations including changes in molecular weight, etc., said conditions being characterized by temperatures above 700 F. and pressures above 1,000 lbs. per sq. in.

I claim: i

1. An improved method for hydrogenating and converting into lighter hydrocarbons highly cracked oils, tars and the like having a marked tendency to coke which comprises heating a stream of such oil with free hydrogen under pressure sufiiciently to effect destructive hydrogenation to a temperature oi. 650 to 750 F., separately heating a second stream of a separate clean oil of less tendency to coke to a temperature of 850 to 950 F. under the same pressure and discharging both oils together into the destruciive hydrogenation zone maintained under the same pressure and a conversion temperature.

2. Method according to claim 1 in which both oils are heated in contact with hydrogen under pressure.

3. In a continuous process for converting hydrocarbon oil tar into gasoline by subjecting said tar to the action of hydrogen at a pressure of the order of 200 atmospheres and at a thermal decomposition temperature, an improvedmethod 110 of operation comprising heating a stream of said tar and hydrogen at said pressure to a temperature above about 650 F. and below that at which coking is pronounced, separately heating a stream of a lighter oil having less tendency to coke and hydrogen to a temperature of about 850 to 950 F., discharging both preheated streams into a reaction zone maintained at a temperature of about 750 to 850 F. and a pressure of about 200 atmospheres and withdrawing a product comprising gasoline from said reaction zone.

4. Process according to claim 3 in which the tar is derived from the products of cracking of petroleum oils 5. Process according to claim 3 in which the reaction zone contains a hydrogenation catalyst. 6. Process according to' claim 3 in which the reaction zone contains a sulfactive hydrogenation catalyst.

7. Process according to claim '3 in which the separately preheated streams are mixed prior to their admission to the reaction zone. 

